fat cat

Short definition from Wiktionary

Noun

1. 1
   A rich person who contributes to a political campaign.
2. 2
   Any affluent person who is perceived to have profited from the labor of others; and/or not to care about those of lesser means.
3. 3
   Used other than figuratively or idiomatically: see fat, cat.
4. 4
   Alternative form of fat cat.